Reheat control arrangement for air conditioning systems



May 25, 1954 w, McGRATH 2,679,142

REHEAT CONTROL ARRANGEMENT FOR AIR CONDITIONING SYSTEMS Filed Sept. 6, 1952 STARTER INVENTOR.

Patented May 25, 1954 REHEAT CONTROL ARRANGEMENT FOR AIR CONDITIONING SYSTEMS William L. McGrath, Syracuse, N. Y., assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Application September 6, 1952, Serial No. 308,224

2 Claims.

This invention relates to a control arrangement for a refrigeration system and more particularly to a control arrangement for a refrigeration system in which the evaporator of the system is employed to condition air.

- The chief object of the present invention is to provide an economical arrangement of a refrigeration system in-which hot gaseous fluid from the compressor is employed to reheat air passing through the evaporator of the refrigeration system.

.An object of the present invention is to provide an air conditioning unit including a refrigeration system, the refrigeration system being so controlled as to cool air passing through the unit when the temperature of ambient atmosphere is high, and to provide reheating for the cooled air when the humidity of the ambient atmosphere is also high.

A further object is to provide a control ar-. rangement for a refrigeration system responsive to temperature and humidity of air being conditioned by the refrigeration system, the control arrangement serving to regulate supply of liquid refrigerant to the evaporator of the refrig-, crating system. and, in response to changing conditions, supplying hot gaseous refrigerant to a portion of the evaporator to heat air cooled bythe rejmainingportions 0f the evaporator.

Other objects of the invention will be readily;

perceived from the following description.

This invention relates to apparatus for condi-L tioning air which comprises, in combination, a

heat exchanger for placing cooling fluid in heat exchange relation with air to be conditioned, means for passing air to be conditioned through the heat exchanger, means for supplying cooling fluid to the heat exchanger, means for supplying,

heating fluid to a portion of the'heat exchanger, control means for controlling the supply of cooling fluid to the heat exchanger and the supply of heating fluid to a portion of the heat exchanger, and regulating means for actuating the meansisin a first position permitting the con-J rected to'evap'oratori.

trohmeans to supply. .cooling fiuid tothe heatexchanger while, when the temperature of the air being conditioned is high and the humidity of the air being conditioned is high, the regulating means is in a second position permitting the control means to supply heating fluid to a portion of the heat exchanger.

The attached drawing illustrates a preferred embodiment of the invention, in which Figure l is a diagrammatic view of a refrigeration system embodying the present invention;

and

Figure 2 is a wiring diagram of the control arrangement of the present invention.

Referring to the attached drawing, there i shown the air conditioning apparatus of the present invention. Figure 1 illustrates a refrigeration system including a compressor 2, actu-' ated by a motor M, controlled by starter S, as hereinafter explained.

Compressor 2 is connected to a condenser 3, which may be air or water cooled. Condenser 3 is connected by line llto an evaporator 5, the usual expansionvalve B is placed in line 4 and is regulated .by bulb 6' in contact with suction line 7.

Evaporator 5 is a sectional evaporator. shown, evaporator 5 contains sections 5a and 5b.; Each of the evaporator sections 5a and 5b is connected'to suction line 1. Expansion valve 6 regulates flow of liquid refrigerant supplied to evaporator 5.. A fan 8 passes air to be conditioned through the evaporator. A reheat line 9 connects compressor 2 with section 517 of the evaporator. Section 5b of the evaporator, as stated above, is connected to, suction line I through line Ill.

ziSolenoid valve H is placed in reheat line 9. Solenoid valve I2 is placed in line It. These valves are provided for a purpose hereinafter described. Energization of the solenoid valves ll, I2 is controlled by means of thermostat T, and humidistat H. Thermostat T and humidi-- stat H are conventional single pole, double throw types. Both thermostat T and humidistat H have two positions designated respectively for purposes of illustration as H and L. Thermostat T and humidistat H are placed, preferably, in the area being conditioned but it will be understood they may be placed if desiredin the path of air di-' ."Con'sideringIFigui-e.2, there is shown theswir ing diagram of the control arrangement of the present invention. Reference will be made to such wiring diagram in connection with the description of the operation of the system described above.

Considering the operation of the system described above, under normal conditions of operation when the temperature is high, refrigerant is compressed in compressor 2 and condensed in condenser 3, supply of the condensed liquid refrigerant to evaporator being regulated by ex pansion valve E. Liquid refrigerant passing into evaporator 5 is placed in heat exchange relation with air to be conditioned, forced therethrough by fan E, the air being cooled and the refrigerant being evaporated and returning to compressor 2 through suction line 'i. Under normal conditions of operation, therefore, solenoid valve i2 is open. and solenoid valve 1 l is closed.

That is, when the temperature is high, a circult is closed from line L2 through the H contact of thermostat T to solenoid valve it to line L3 which opens the valve, assuming the comressor is in operation. valve ii remains closed since the thermostat contact L of thermostat T is broken. The position of humidistat E is immaterial, under these conditions of operation, for thermostat T controls operation of the reirigeration system.

, Assume, however, that the temperature has decreased, while the humidity of the air being treated is high; under such conditions of op eration, a circuit is completed from the starter coil through contact H of the humidistat H, then through the selector switch to L2, so that the compressor of the machine remains in operation. A second circuit is completed from line L2 through the L contact of thermostat T to sole noid valve and line L3 energizing valve 1 i. Solenoid valve I2, is not energized since the L contact of humidistat H is broken so that valve [2 is closed. Under these circumstances, the compressor continues in operation supplying liquid refrigerant to section 5a of evaporator 5. Solenoid valve ii being open permits hot gaseous refrigerant to be supplied to section 51) of evaporator 5. Thus air passing through the evaporator is placed in heat exchange relation with liquid refrigerant in section 511, cooling the air and evaporating the refrigerant, while in section 532, the cooled air is heated by the hot gaseous refrigerant therein. The hotgaseous refrigerant in section 519 is condensed by its heat exchange relation with the cooled air and flows through feed line 23 to section 5a, being evaporated therein, the gaseous refrigerant returning to the compressor through suction line I.

present invention provides a simple arrangement to control temperature and humidity of air being conditioned. As described above, when the temperature and humidity of the air being conditioned are both high, the air is cooled but no reheat is supplied. When the temperature is high and the humidity is low, the air is cooled only. When the temperature is low (any predetermined point) and the humidity is high the air is cooled to reduce the humidity and reheated to achieve comfortable conditions. Of course, when both temperature and humidity of the air is low, the system is not in operation since the circuit to the starter coil is not closed and hence the compressor and the refrigeration system is not in operation.

While I have described temperature and .hu--

midity of air being conditioned as high and low,

it will be understood any desired temperatures or humidities or" the air being treated may be selected, these terms being used to describe two predetermined temperatures or humidities which, of course, are selected by the operation in which the control arrangement is employed.

While the control arrangement of the present invention is illustrated in connection with an evaporator separated into sections, it will be appreciated it may be applied in connection with a separate reheat coil or if desired a condenser water reheat coil. In the present invention, the separate valves act in effect as a three-way valve and such a valve, of course, may be used in place of these valves.

While I have described a preferred embodiment of my invention, it will be understood my invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. In apparatus for conditioning air the combination of a heat exchanger for placing cooling fluid in heat exchange relation with air to be conditioned, means for passing air to be conditioned through the heat exchanger, means for supplying cooling fluid to the heat exchanger, means for supplying heating fluid to a portion of the heat exchanger, a first control member for controlling supply of cooling fluid to the heat exchanger, a second control member for controlling supply of heating fluid to a portion oi. the heat exchanger, regulating means for actuating the control members in accordance with conditions of temperature and humidity of the air being conditioned, said regulating means being so constructed and arranged that, when the temperature of the air being conditioned is high, the regulating means is in a first position and the first control member permits supply of cool ing fluid to the heat exchanger while, when the temperature of the air being conditioned is low and the humidity of the air being conditioned is high, the regulating means is in a second position to move the first control member to a closed position discontinuing the supply of cooling fluid to the portion of the heat exchanger and to move the second control member to a first position permitting supply of heating fluid to that portion of the heat exchanger, said regulating means comprising a two-position thermostat responsive to two pie-determined temperature conditions of air being conditioned and a two-positioned humidistat responsiveto two predetermined humidity conditions of air being conditioned, the thermostat and the humiclistat being so connected to each other and the control members that cooling fluid is supplied to the heat exchanger when the thermostat is in a first position regardless of the position of the humidistat while, when the thermostat is in a second position, heating fluid is supplied to a portion of the heat exchanger when the humidistat is in a first position.

2. A control arrangement for an air-conditioning system which comprises control means for controlling supply of cooling medium in heat exchange relation with air being conditioned and supply of heating medium in heat exchange relation with air being conditioned and regulating means for regulating the control means in accordance with desired conditions of temperature and humidity whereby the regulating means. is. in a first position when the temperature of;

the air being conditioned is high permitting the control means to supply cooling fluid in heat exchange relation with air being conditioned while, when the temperature of the air being conditioned as low and the humidity of the air being conditioned is high, the regulating means is in a second position permitting the control means to supply heating fluid in heat exchange relation with the cooled air, said regulating means comprising a two-position thermostat re-. sponsive to two pre-determined temperature conditions of air being conditioned and a two-position humidistat responsive to two ire-determined humidity conditions of air being conditioned, the thermostat and the humidistat being so connected to each other and the control means that cooling fluid is supplied to the air being conditioned when the thermostat is in a first position References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,172,877 Parcaro Sept. 12, 1939 2,195,781 Newton Apr. 2, 1940 2,451,385 Groat Oct, 12, 1948 OTHER REFERENCES Reheating By Means of Refrigerant Compressor Discharge Gas, by S. F. Nicoll, pp.

736-741 of Heating, Piping and Air Conditioning, December, 1940. 

